Page 47 - 6273

the ratio of the magnitudes of electronegativity, the atoms can have both a positive

and a negative oxidation state. The positive oxidation state is equal to the number

of electrons displaced from this atom. The negative oxidation state is equal to the

number of displaced electrons in this atom. The oxidation states are indicated by

Arabic numerals with a plus or minus sign before the digit and placed at the top of

the element symbol, for example: , , , , , . This refers

to the oxidation state of atoms in the formulas of compounds, in particular in redox

reactions. In addition, the oxidation state is also indicated by Roman numerals in

parentheses after the symbols of the elements or their names, for example: Mn (II),

Co (III), phosphorus (V), manganese (VII). This form used in the preparation of

compounds or names in the text.

In contrast to the oxidation state the charges of the ions in compounds are

indicated by the Arabic numerals with plus or minus sign after the number, for

example: , , – , . The magnitude and sign of the oxidation states of

atoms in compounds is determined according to:

1) in neutral molecules and crystals the algebraic sum of the oxidation states

of all atoms is equal to zero;

2) the oxidation state of Oxygen in its compounds is -2. The exceptions are

 1
peroxide compounds, where Oxygen oxidation state is -1 ( Na O 2 ),
2

superoxides ( ), ozonide( ) and fluoride ( ). In the latter

compounds the Oxygen has a positive oxidation state;

1) the oxidation state of Hydrogen in all compounds with nonmetals is + 1.

However, in metal hydrides ( , the oxidation state of Hydrogen is -

1;

4) Fluorum as the most electronegative element in all compounds has the

oxidation state of -1;

5) the oxidation state of alkali metals in all compounds is +1, and alkaline

earth +2.

47